Letter to the Editor

Nowadays, the invasive approach plays a crucial role in the management of acute coronary syndromes, according to the recommendations in clinical practice guidelines. This tendency was reflected in some papers published in Revista Española de Cardiología in 2011 and 2012. Regarding ST-segment elevation acute coronary syndromes, regional programs on primary coronary angioplasty have been developed across Spain. Time delay until reperfusion, however, remains the main drawback of these programs. For instance, Badalona's experience shows that in only 27% of the patients transferred from other hospitals for primary angioplasty the coronary artery was opened within the time limits recommended in the guidelines, i.e. in less than 2 hours from the first medical contact 1. Therefore, fibrinolysis should not be ruled out as an alternative treatment in some cases. Furthermore, data from cardiac magnetic resonance imaging did not evidence significant differences in left ventricular volumes and function between patients treated with primary angioplasty or pharmaco-invasive strategy (initial fibrinolysis followed by routine coronary angioplasty 24 hours later) in a single hospital registry 2. Prediction of prognosis is a matter of concern. The 4 most known prognostic scores (TIMI, PAMI, CADILLAC and GRACE) were compared in patients managed with either primary or rescue coronary angioplasty 3. All 4 scores (particularly TIMI, CADILLAC and GRACE) had an excellent accuracy to predict mortality at 30 days and 1 year; prediction of reinfarction or new revascularization, however, was very poor with any score. The invasive management has been extended to populations previously excluded from this treatment, such as elderly patients. In a retrospective study on very old patients (≥ 85 years) with non-ST-segment elevation acute coronary syndrome, the invasive approach reduced mortality and any ischemic event at 3 years compared with a matched population managed with a conservative strategy 4. Despite the favorable results of the invasive strategy in any type of acute coronary syndrome, secondary prevention should not be overlooked. In this sense, the opening of a cardiac catheterization laboratory and the subsequent increase of coronary intervention procedures for myocardial infarction, improved mortality at 30 days but not between 30 days and 2 years after adjusting for ACE inhibitor, beta-blocker and statin treatment 5 .


Letter to the Editor
We have read with great interest the article by Moghadam et al. [1] and we found the study interesting because the authors appropriately dealt with the sealing properties of the Calcium Enriched Mixture and Mineral Trioxide Aggregate used as cervical barriers during the treatment of tooth whitening. It is known that the filtration of hydrogen peroxide in the periodontal space can cause root resorptions at the cervical level [1], therefore it is important to have performed the evaluation in question. However, we would like to comment on a few methodological aspects wish might benefit futures related studies.
Currently there is controversy regarding the measurement of filtration. Although no consensus has been reached on the most appropriate technique for the evaluation of this filtering process, it is known that some methods such as bacterial penetration, fluid filtration and glucose penetration model presents more real results and have less disadvantages for measurement.
Various investigations indicate that the penetration of dyes presents inconveniences by a possible effect of entrained air at the entrance of the dye solution. Previous studies have shown that at normal atmospheric pressure, the effect of air trapped along the margin of the root canal can impede the flow of penetration [2,3]. Thus, a high degree of variation has been found in the results of penetration, when the same materials and methods were used with different atmospheric pressures [4]. In order to solve this effect, it is recommended to follow the vacuum methodology, in which a partial pressure is applied which facilitates the penetration of the coloring agent [2,4].
Furthermore, to perform measurements of dye penetration in millimeters, the teeth were cut longitudinally using diamond discs 0.1 mm in diameter. This procedures present also disadvantages, because it is possible that part of the sample is eliminated and consequently, part of the measurement can be lost. A procedure that could prevent these drawbacks is the diaphanization. This technique allows to obtain a three-dimensional view of the root canals. In addition, in comparison to the conventional process of dye penetration measurement, the diaphanization has the advantage of not requiring cutting and practice to perform an evaluation in the three dimensions of the tooth [5].
We hope these recommendations will contribute to enrich future related studies and to better understand the methods used to assess the microleakage of different materials.

Authors Reply
Thanks for reading and commenting on our manuscript. Here are the comments and some responses to them:

1.
Currently there is controversy regarding the measurement of filtration. Although no consensus has been reached on the most appropriate technique for the evaluation of this filtering process, it is known that some methods such as bacterial penetration, fluid filtration and glucose penetration model presents more real results and have less disadvantages for measurement.

Response:
We agree with your comment; however we chose dye penetration in this study since it is a simple and useful method based on chemical color reaction and it has been used in several studies [1,2]. Also as it was mentioned there has been no agreement about the standard technique for evaluation of sealing properties of materials. Furthermore, other methods have some disadvantages, for example, special species or a limited number of bacteria are used in bacterial leakage tests, therefore it doesn't provide the real clinical condition. Moreover, bacterial synergistic effect, influence of environment, thermal changes, salivary enzymes, buffering materials and antibodies are neglected in bacterial leakage studies [3].

2.
Various investigations indicate that the penetration of dyes presents inconveniences by a possible effect of entrained air at the entrance of the dye solution. Previous studies have shown that, at normal atmospheric pressure, the effect of air trapped along the margin of the root canal can impede the flow of penetration. Thus, a high degree of variation has been found in the results of penetration, when the same materials and methods were used with different atmospheric pressures. In order to solve this effect, it is recommended to follow the vacuum methodology, in which a partial pressure is applied which facilitates the penetration of the coloring agent.

Response:
It is true that the air trapped along the margin of root canal can impede the flow of penetration, but there is no consensus about the atmospheric pressure in which the dye penetration test should be done. Also no studies have been recommended the standard conditions such as atmospheric pressure to do the dye penetration test.
3. Furthermore, to perform measurements of dye penetration in millimeters, the teeth were cut longitudinally using diamond discs of 0.1 mm in diameter. This procedures present also disadvantages, because it is possible that part of the sample is eliminated and consequently, part of the measurement can be lost. A procedure that could prevent these drawbacks is the diaphanization. This technique allows to obtain a three-dimensional view of the root canals. In addition, in comparison to the conventional process of dye penetration measurement, the diaphanization has as main advantage that it does not require cutting and practice to perform an evaluation in the three dimensions of the tooth.